The study of the mechanisms of plant defense reactions during pathogenesis is closely related to the elucidation of the role of chloroplasts as intracellular sensors that sensitively respond to external stimuli. An important criterion for assessing the severity of development of the pathological process in plants is the amount of chlorophyll, which is determined by the balance between the processes of biosynthesis and breakdown of pigment molecule in the plant cell. The objects of the study were the seedlings of spring barley (Hordeum vulgare L.) chaffy variety Raider of Belarusian selection. Seedlings of different ages (3-, 7-, and 10-day-old) were infected with spores of the fungus Bipolaris sorokiniana (Sacc.) Shoem., the causative agent of helminthosporiosis. Forty-eight hours after inoculation, an analysis of the initial stages of chlorophyll degradation was carried out based on the activity of the main hydrolytic enzyme, chlorophyllase, and the content of chlorophyllide and pheophytin in the primary barley leaves. Ontogenetic differences in the degradation process of phytol-containing chlorophyll pigments, as well as an increase in chlorophyllase activity and the degree of pheophytinization of pigments under the influence of the pathogenic fungus B. sorokiniana were discovered. Pigment indicators such as the content of phytolic and non-phytolic forms of chlorophyll and the content of pheophytin can be used as criteria for the early diagnosis of barley plant damage by a fungal pathogen and for assessing the degree of degree of infection.

The expression levels of the CBF3, CBF15.2, CBF19, and CBF21 genes were studied using real-time PCR under simulated cold stress conditions in winter wheat varieties Irkutskaya, Girlyanda, and Cubus, which exhibit different levels of frost resistance. It was shown that the CBF3 gene is not expressed at +4 °C. Its expression level increases as the temperature decreases to –4 °C and reaches a maximum in the Girlyanda variety, exceeding the control values by 407.24 and 363.13 times after 2 and 24 hours, respectively. Two main expression peaks were revealed for the CBF15.2 gene in all studied varieties: at 2 hours after temperature decrease to –2 °C and –4 °C, respectively. The CBF19 gene expression profile was characterized by the most pronounced response to cold stress in the studied varieties when the temperature decreased to +4 °C, and 24 hours later when it decreased to –2 °C in the Irkutskaya and Cubus varieties. The greatest increase in the CBF21 gene expression level (44.61 times) was revealed for the Girlyanda variety 24 hours after the temperature decreased to –2 °C. The results show that the gene expression level increased at both the initial (CBF19 and CBF21 genes), intermediate (CBF3, CBF15.2, CBF19 and CBF21 genes) and final stages (CBF3 and CBF15.2 genes) of cold stress modeling. It depends on the genotype and is generally higher in the winter-hardy Girlyanda variety. The results can be used to assess the potential of wheat accessions to tolerate cold stress.

The effect of seed treatment with chitosan ferulic acid (Ch30-FA) or caffeic acid (Ch30-CA) conjugates on biometric parameters and pro-/antioxidant system activity in spring barley seedlings (Hordeum vulgare L.) was studied under optimal conditions, salt stress, and subsequent recovery. The Ch30-CA conjugate exerted a mild stress effect, triggering compensatory mechanisms that include activation of cellular repair processes and, likely, de novo enzyme synthesis. Treatment with chitosan–hydroxycinnamic acid conjugates, especially Ch30-CA, contributed to sustained high activity of antioxidant enzymes (SOD, POD, APX, GR) and low hydrogen peroxide accumulation in the roots and leaves of barley seedlings under salt stress and during the recovery period. This phenomenon resulted in enhanced adaptive response and accelerated growth of barley seedlings. Differences in the effects of the two conjugates on plants were observed. When applied during the transition from short-term salt stress to the post-stress period, the Ch30-FA conjugate reduced proline content in the leaves, whereas treatment with the Ch30-CA conjugate increased proline content. During the recovery period, POD and GR activities in the leaves increased under Ch30-CA treatment compared to salt stress, while they remained almost unchanged in leaves of plants treated with Ch30-FA.

The study examines the fungistatic effect of bark extracts from Frangula alnus Mill. and Rhamnus cathartica L. on representatives of the phylum Basidiomycota – phytopathogens and xylotrophs that cause damage to forest crops and wooden structures. Six fungal strains from the Belarus Collection of Non-pathogenic Microorganisms of the Institute of Microbiology of the NAS of Belarus were investigated in the experiment: Phellinus igniarius (BIM F-205), Phellinus tremulae (BIM F-204), Fomitopsis pinicola (BIM F-225), Phellinus pini (BIM F-321), Gloeophyllum sepiarium (BIM F-227), and Serpula lacry­ mans (BIM F-835). The results showed that the F. alnus extract, containing hydroxyanthraquinone secondary metabolites, signi ficantly suppressed the growth of five out of the six species, with the strongest effect observed for S. lacrymans (57 % inhibition). Further analysis using extracts with varying concentrations of hydroxyanthraquinones revealed a clear dose-dependent response in G. sepiarium, confirming the key role of these compounds in the fungistatic effect. The findings expand the understanding of the role of hydroxyanthraquinones in phytoimmunity and open prospects for their application in forest crop biotechnology.

The transboundary sections of the Neman and the Chornaya Hancha rivers located on the territory of Belarus were studied. A total of 143 identified lower detectable taxa (LDT) of macrozoobenthos were recorded in quantitative samples, of which 116 were identified to the species level, and 12 LDT in qualitative samples, of which 11 were identified to the species level. The identified animals belong to three phyla of aquatic invertebrates: Mollusca – 25 LDT, Annelida – 11, and Arthropoda – 107. The highest mean values of species richness (44 LDT) and abundance (384.6 ind/m²) were recorded for the Neman River near to Mosty Levye village. Three alien species were detected (Lithoglyphus naticoides (C. Pfeiffer, 1828); Dikerogammarus haemobaphes (Eichwald, 1841)); Faxonius limosus (Rafinesque, 1817)). Species protected in Belarus were recorded, such as dragonflies Anax imperator Leach, 1815 and Gomphus flavipes Charpentier, 1825.

This study examines the spatial distribution of Siberian flying squirrel (Pteromys volans L.) habitats in the Be - larusian Lake Region using geographic information systems. The analysis incorporates field survey data collected during 2024–2025 and forest inventory records from 16 study plots. The flying squirrel was consistently recorded on these plots throughout the entire observation period. Twelve sites are located in the Gorodok District and four are in the Vitebsk District. The flying squirrel predominantly inhabits mixed forests of the bog bilberry and wood-sorrel forest types. These forests occur on moist, nutrient-rich soils and are characterized by high site quality (Bonität class I–II) and moderate stand density (0.6–0.8). The mean age of the dominant tree species (aspen, birch, spruce) exceeds 60 years. Their mean age is over 60 years old. Mature aspens aged 70–85 years play a crucial role for the species, providing nesting sites. A positive but weak correlation was found between aspen proportion in stand composition and flying squirrel occurrence (Spearman’s rank correlation coefficient r_s = 0.30). Surveys were conducted in Liozna and Orsha Districts, where pronounced forest fragmentation occurs. No evidence of P. volans presence was found in these areas, despite certain forest compartments meeting the species’ habitat requirements. The current southern range limit of the Siberian flying squirrel in Belarus is confined to Vitebsk District, where extensive and ecologically resilient forest complexes remain intact.

A histological and electron microscopic study of the caudal fin structure of sub-adult blue gourami (Trichogaster trichopterus Pallas) was conducted. It was found that on frontal sections of the organ, the appearance of both lepidotrichia and other structures differs significantly in its proximal, central and distal parts. The proximal part of the fin contains scales and interradial muscles, the central part contains only scales, and the aforementioned structures are absent distally. It was confirmed that the mechanical support of the caudal fin of gourami is provided not only by the set of lepidotrichia, but also by the associated interlayer system of collagen fiber, which are located in the space of loose connective tissue, connecting with the dermis and hemitrichia. In the interhemitrichial space, in the areas of the organ located both in its middle and at the distal edge, there are dense groups of specific fibroblasts, most of which are large in size, polygonal in shape, with large nuclei and clear cytoplasm. The following cells with centrioles have been identified in the caudal fin of gourami: epidermocytes of the basal and suprabasal layers of the epidermis, fibroblasts of connective tissue, Schwann cells, endothelial cells, myo- satellite cells, and large fibroblasts of the interhemitrichial space.